THE THEORY OF DESCENT 255 



the diversities. The similarities now are " explained " ; 

 that is to say, they are understood as resting on but one 

 principle : the similarities are understood as being due to 

 inheritance ; 1 and now we have but one problem instead 

 of an indefinite number. For this reason Wigand granted 

 that the theory of descent affords what he calls a numerical 

 reduction of problems. 



Understanding then what is explained by the theory 

 of descent with its necessary appendix, we also understand 

 at once what is not elucidated by it : the diversities of the 

 organism remain as unintelligible as they always were, 

 even if we know that inheritance is responsible for 

 what is similar or equal. Now there can be no doubt 

 that the diversities are the more important point in 

 systematics ; if there were only similarities there would 

 be no problem of systematics, for there would be no system. 

 Let us be glad that there are similarities in the diversities, 

 and that these similarities have been explained in some 

 way ; but let us never forget what is still awaiting its 

 explanation. Unfortunately it has been forgotten far too 

 often. 



THE SMALL VALUE OF PURE PHYLOGENY 



And so we are led to the negative side of the theory 

 of transformism, after having discussed its positive half. 

 The theory of descent as such, without a real knowledge 



1 It seems to me that my argument gives a broader logical basis to the 

 theory of descent than does that of G. Wolff (Die Beyriindung der 

 Abstammungslehre, Miinchen, 1907). Wolff starts from the concept of 

 organic teleology, and thus finds the only reason for accepting the theory 

 of transformism in the existence of so-called "rudimentary organs" ; these 

 organs would form an obstacle to teleology if they could not be regarded 

 as inherited. 



